In a power conversion apparatus such as an inverter integrated into a motor, the electrodes of semiconductor devices included in the power conversion apparatus are electrically connected with other circuit components using a bus bar, as disclosed in Japanese Patent Laying-Open Nos. 2006-262664, 2004-364427, 2004-040877, 2005-261035, and 2006-074918.
In particular, Japanese Patent Laying-Open No. 2006-262664 discloses a power conversion apparatus suitable for motor drive of a hybrid vehicle, in which the top and bottom surfaces of such a structure as an inverter including semiconductor devices and bus bars are laminated with insulating films so that a plurality of semiconductor devices and circuits are collectively insulated. In particular, in a structure disclosed in Japanese Patent Laying-Open No. 2006-262664, electrodes of semiconductor devices and bus bars are directly connected with each other without bonding wire. Japanese Patent Laying-Open No. 2004-364427 discloses that bus bars are connected to both surfaces of a semiconductor device in order to establish electrical connection.
However, in the structure in which an electrode of a semiconductor device and a bus bar are directly connected with each other as disclosed in Japanese Patent Laying-Open Nos. 2006-262664 and 2004-364427, the bus bar is thermally expanded due to a temperature rise resulting from current passing or heat from the semiconductor device, so that thermal stress acts on a connection portion. Considering that a temperature rise is relatively large in an inverter having a bus bar connected to a plurality of semiconductor devices and that size reduction is demanded for a high-power, power conversion apparatus typically applied to a vehicle, such an interconnection structure is requested that can stably secure electrical connection between an electrode of a semiconductor device and a bus bar even at a temperature rise.